Dr. Kassai Tibor - Dr. Murai Éva szerk.: Parasitologia Hungarica 10. (Budapest, 1977)
Parasit. Hung 10. 1977. Comments on the Nature and Methods of Collection of Fish Coccidia Dr. Kálmán MOLNÁR Research Institute for Veterinary Science, Hungarian Academy of Sciences, Budapest "Comments on the nature and methods of collection of fish coccidia. " - Molnár, K. - Parasit. Hung. _10. 41-45. 1977. ABSTRACT. Eimerian species of fish are little studied owing to the difficulties in their recovery and storage. Common separation procedures usually injure the extremely thin and vulnerable wall of the oocyst. For the detection of intestinal fish coccidia native investigation of the intestinal content (faeces), intestinal mucus and mucosal scrapings is recommended, while the species localizing in the tissues should be separated by digestion with 0.25-0.5% trypsin solution. Stable microscopic preparations can be made from samples of faeces, mucus or tissues spread on a slide by compression with a coverslip and by the instillation of 4% formaline or 2.5% glutaraldehyde and sealed with Canada balsam. Up to now about 100 Eimeria species have been described from fish, above all from freshwater hosts. This is a very low number compared to the number of coccidian species known in warm-blooded animals. PELLÉRDY's monograph (1974) includes the description of 75 fish coccidia, since then about two dozen new species were described mostly by the present writer and his coworkers (MOLNÁR and FERNANDO, 1974; MOLNÁR and HANEK, 1974). Coccidia are only infrequently dealt with in papers on the incidence and dynamics of fish parasites, although according to our own experiences, Eimeria species can be collected from fish hosts relatively easily by aimed investigation. Since the main reason of the apparently limited interest in Eimerian parasites of fish seems to be the inadequacy of methodical approach, some aspects facilitating the study of fish coccidia will be outlined in this paper. Main characteristics of fish coccidia Eimerian parasites of fish differ from those of mammals and birds in certain morphological and developmental aspects, but attempts for classification of the genus Eimeria, including the segregation of fish Eimeriae (LABBE, 1893; PELLÉRDY, 1964) have failed for lack of feasible differentiating features. Thus in the foHowing description of those features of fish Eimeriae will be given, which facilitate the detection and collection of these parasites. 1, Most Eimeria species living in fish are passed by the host in a sporulated state. This is a fairly general rule with fish coccidia, although there are some exceptions, such as Eimeria pigra and E. aurati, which undergo sporulation outside the host, or E. micropteri , most oocysts of which become extruded in a semi-sporulated state. 2. Since abrupt environmental changes are not common in the aqueous habitat, the coccidia of fish are less resistant to external influences than those of other host species. Low resistance is obviously due to the thinness of the shell of both oocyst and sporocyst. The approx. 30 species studied by the present writer all had an unilayered wall. x The thickness of the X In the drawings presented with related publications (PELLÉRDY and MOLNÁR, 1968; MOLNÁR and PELLÉRDY, 1970) and in PELLÉRDY 's monograph (1974) as well, the depiction of the oocyst wall is faulty, showing it to be thicker than it is in reality, although the description of it is correct.
